The disclosed invention relates to use of steel mill oily sludges and steelmaking slag fines in the preparation of a material useful in the preparation of a base for roadways, parking lots, walkways, foundations, dikes, railroad tracks and the like. More particularly, the disclosed invention intermixes steel mill oily sludge and steelmaking slag fines through high energy shear mixing in order to create an intermediate material. The intermediate material may thereafter be mixed with pozzolonic binders, such as cement, fly ash, and asphaltic emulsion in order to create a roadway base material that is overlaid onto a sub base. The resulting base exhibits relatively high strength, minimizes cracking due to the xe2x80x9cfreeze/thawxe2x80x9d cycle, and is able to withstand the long term deleterious effects attributable to high weight trucks and the like traveling over the finished roadway.
A typical roadway is formed by preparing the earth by grading, scraping, and the like in order to provide a relatively flat surface upon which the roadway is to be formed. Most roadways have a sub base formed of stabilized sand or soil and a base formed of crushed rock, crushed concrete, or other stabilized materials that support the overlying roadway. Concrete, macadam, and the like overlie the sub base in order to provide the roadway.
A typical roadway is exposed to accumulations of water because of either the proximity of subsurface water or pooling that occurs due to storms, runoff, and the like. The water has a tendency to wash out the soil supporting the base, thus weakening the sub base and its overlying roadway or base. In addition, in those areas subject to the xe2x80x9cfreeze/thawxe2x80x9d cycle, unacceptable cracking may occur. When a base course cracks, typically because of inflexibility or inelasticity (which is measured by flow), the crack transmits through the surface course. Water then invades the crack. The freeze/thaw cycle expands the crack and leads to early failure of the roadway, parking lot, etc.
Attempts have been made to alleviate the problems attributable to water accumulation, but they have not been successful and frequently are expensive. Similarly, attempts have been made to overcome the problems of the freeze/thaw cycle, but they likewise have not been successful. For example, asphaltic emulsion frequently is applied to the exposed surface of a roadway in an attempt to seal it against moisture. Gravel and other relatively fine materials sometimes are applied to the asphaltic emulsion in order to minimize slickness. Asphaltic emulsion and the application of fine gravel increased the cost of maintaining a roadway, and generally have not been successful.
The disclosed invention meets these and other needs in the art by providing a roadway base that is formed from oily sludge created in a steelmaking plant, and steelmaking slag fines. The oily sludge and slag fines are mixed together in a high energy, shear mixer, and allowed to set for a sufficient period to cause the water in the sludge to hydrate the lime in the slag fines. After the lime has been hydrated, then the resulting intermediate product is mixed with pozzolonic binders, such as cement and fly ash and non-pozzolonic binders such as asphaltic emulsion, and mixtures thereof, in order to provide a base of relatively high strength and increased water resistance which substantially reduces the detriments of the freeze/thaw cycle.
A roadway base intermediate, according to the invention, comprises oily sludge and steelmaking slag fines.
A roadway base intermediate according to the invention consists essentially of oily sludge and steelmaking slag fines.
According to the invention, a method of preparing a roadway base intermediate comprises the steps of providing a supply of water-containing oily sludge. A supply of lime containing steelmaking slag fines is provided. The oily sludge is then blended with the steelmaking slag fines. The blended oily sludge and slag fines are allowed to react for a period sufficient to hydrate the lime.
A roadway base according to the invention, comprises oily sludge, steelmaking slag fines, and pozzolonic binder selected from the group consisting of cement, and fly ash and non-pozzolonic binders such as asphaltic emulsion, and mixtures thereof.
A method of preparing a roadway base comprises the steps of providing a supply of water-containing oily sludge and a supply of lime-containing, steelmaking slag fines. The sludge and the slag fines are blended. The blended sludge and slag fines are allowed to cure for a period sufficient to hydrate the lime. The hydrated blended sludge and slag fines are mixed with pozzolonic binder selected from the group consisting of cement, and fly ash and non-pozzolonic binders such as asphaltic emulsion, and mixtures thereof
These and other objects and advantages of the invention will be readily apparent in view of the following description and drawings of the above-described invention.